Objectives Styrene was incorporated in the 12^th Report on Carcinogens (RoC) based on sufficient experimental evidence in animals. The human evidence has been evaluated as limited by RoC and IARC. The objective of this study was to analyse the risk of haematopoetic malignancies and other cancers following occupational styrene exposure.

Method The cohort consists of 74 902 workers (84% men) in the Danish reinforced plastics industry, originating from 481 companies ever producing reinforced plastics in Denmark 1964–2009. We identified all workers in the National Supplementary Pension Fund Registry for which all employees are compulsory members. Cancer diagnoses were found in the National Cancer Registry. Standardised Incidence Rate Ratios (SIRs) and 95% confidence intervals (95% CI) were used for relative risk estimation.

Results Among the 74 902 workers, we identified 10 374 cases of cancer accumulating 1.5 million person years. The overall SIR was 1.00 (95% CI 0.98–1.02). SIR for lymphatic and haematopoietic cancers was 0.99 (0.91–1.07). Among male workers we observed increased risk of buccal cavity and pharygeal cancers (SIR 1.24; 1.12–1.37), cancers of the respiratory system (SIR 1.33; 1.26–1.39), and bladder cancer (SIR 1.08; 1.0–1.17), and among female workers cancers of the respiratory system (SIR 1.41; 1.22–1.62).

Conclusions The cohort experiences the same overall cancer risk as the general population and no increased overall risk of malignant haematopoietic diseases was apparent. However, we observed increased risks for cancers that may be due to confounding from smoking and alcohol. Internal risk assessment that includes historical styrene exposure data will supplement the current findings.